mud flow

Sidoarjo mud flow

The Sidoarjo mud flow or Lapindo mud, also informally abbreviated as Lusi, a contraction of Lumpur Sidoarjo (lumpur is the Indonesian word for mud), is a since May 2006 ongoing eruption of gas and mud in the subdistrict of Porong, Sidoarjo in East Java, Indonesia (20 kilometers south of Surabaya). It is considered to be a mud volcano. It appears that the flow will continue indefinitely and so far all efforts to stem the flow have failed.

Geological setting

Mud volcano systems are fairly common on Earth, and particularly in East Java province. Beneath the island of Java is a half-graben lying in the east-west direction, filled with overpressured marine carbonates and marine muds. It forms an inverted extensional basin which has been geologically active since the Paleogene epoch. The basin started to become overpressured during the Oligo-Miocene period. Some of the overpressured mud escapes to the surface to form mud volcanoes, which have been observed at Sangiran Dome and near Purwodadi city (200 km or west of Lusi).

The East Java Basin contains a significant amount of oil and gas reserves and therefore the region is known as a major concession area for mineral exploration. The Porong subdistrict, 14 km south of Sidoarjo city, is known in the mineral industry as the Brantas Production Sharing Contract (PSC), an area of approximately 7,250 km² which consists of three oil and gas fields: Wunut, Carat and Tanggulangin. As of 2006, three companies — Santos (18%), MedcoEnergi (32%) and PT Lapindo Brantas (50%) — had concession rights for this area; PT Lapindo Brantas acted as an operator.

Mud eruption chronology

On May 28, 2006, PT Lapindo Brantas targeted gas in the Kujung Formation carbonates in the Brantas PSC area by drilling a borehole named the 'Banjar-Panji 1 exploration well'. In the first stage of drilling the drill string first went through a thick clay seam (500–1,300 m deep), then sands, shells, volcanic debris and finally into permeable carbonate rocks. at this stage the borehole was surrounded by a steel casing to help stabilise it. At 5:00 a.m. local time (UTC+8) a second stage of drilling began and the drill string went deeper, to about 2,834 m (9,298 ft), this time without a protective casing, after which water, steam and a small amount of gas erupted at a location about 200 m southwest of the well. Two further eruptions occurred on the second and the third of June about 800–1000 m northwest of the well, but these stopped on June 5, 2006. During these eruptions, hydrogen sulphide gas was released and local villagers observed hot mud, thought to be at a temperature of around .

From a model developed by geologists working in the UK, the drilling pipe penetrated the overpressured limestone, causing entrainment of mud by water. The influx of water to the well bore caused a hydrofracture, but the steam and water did not enter the borehole; they penetrated the surrounding overburden and pressured strata. The extra pressure formed fractures around the borehole that propagated 1-2km to the surface and emerged 200 m away from the well. The most likely cause of these hydraulic fractures was the unprotected drill string in the second stage of drilling. Borehole protection by steel casing is a common procedure in oil or gas exploration.

Impact

The daily flow was estimated at 7,000–150,000 m³. By early September 2006 a hot torrential mudflow had inundated rice paddies and villages, covering an area of approximately 240 ha and resulting in the displacement of more than 11,000 people from eight villages in the Porong subdistrict. Twenty-five factories had to be abandoned, rice fields and fish and shrimp ponds were destroyed, which further threatened Sidoarjo's status as the biggest shrimp producer in Indonesia after Lampung. The Marine Resources and Fisheries Ministry has estimated a financial loss of 10.9 billion rupiahs (US$ 1.2 million) to the fisheries business in Tanggulangin and Porong subdistricts. PresidentSusilo Bambang Yudhoyono declared the 400 ha area inundated by the mud flow as a disaster-prone area unfit for human habitation. As a consequence, 2,983 families had to be relocated to safer places.

On November 23, 2006, eleven fatalities were reported from the explosion of a gas pipe caused by the mud flow. The accident occurred due to significant subsidence of the ground, up to 2 m (6.5 ft), due to the outflow of mud causing a dyke to collapse resulting in the rupture of the state-owned Pertamina gas pipeline. The gas sent flames into the sky and according to the local people, the heat could be felt one kilometer (0.6 miles) away.

As of December 2007 the total volume of expelled mud was estimated at over 28,000 m³, covering an area of , burying eleven towns and displacing at least 16,000 people. It is expected that the mud eruption will last for years to come and the area will experience a significant depression, forming a large caldera.

Transportation and power transmission infrastructure has been damaged extensively in the area. Speaking in front of the People's Representative Council, the house speaker Agung Laksono declared that the state will need to finance the infrastructure repairs, while PT Lapindo Brantas will be responsible for financing the ongoing mitigation effort and also to pay 2.5 trillion rupiah as compensation to the victims. The Porong-Gempoltoll road in East Java province has been significantly damaged by the mud flow and is practically inoperable. The chairman of the national team handling the disaster, Basuki Hadimuljono, indicated that a 12 km long, 120 m wide, corridor will be acquired to the west of the affected area in which to rebuild the turnpike and also to construct a new rail line and gas pipeline to replace the disrupted links. These costs will be carried by the public sector.

Mitigation

A network of dams and barriers has been erected to contain the mud. On September 26, 2006 a barrier failed, resulting in the flooding of more villages. Further strengthening of the dam system appeared to contain the sludge and no further reports of breaches were received until January 4, 2008 when a dyke collapsed after a dispute with a landowner prevented reinforcement before the onset of the rainy season.

Ideas have been submitted for the constructive use of the mud for example as bricks and other building material. The heat of the process may also be usable for thermal energy.

There has been an effort to stop and/or lessen the effects of the mud flow through the dropping of chains of concrete balls into the crater. The hope is to shrink the size of the evacuation tube and thus slow the rate of flow. This plan has been criticised for potentially inducing further flows to the surface in an area already severely weakened rather than succeeding in stemming the flow.
The first series of concrete balls was lowered into the mud volcano on February 242007. It was planned to deployed up to 1500 such balls.
On March 19 2007, after hundreds of balls had been dropped into the mouth of the hole, the flow of mud stopped for a period of 30 minutes.

Drilling operations have been seriously hampered, with continual delays forced upon the relief well drilling team due to lack of funding. Drilling operations have been suspended until the implementation of the National Government Team's plan to plug the flow with the concrete balls.

Investigation

Cause

There is controversy as to what triggered the eruption and whether the event was a natural disaster or not. According to PT Lapindo Brantas it was the May 2006 earthquake that triggered the mud flow eruption, and not their drilling activities.
Two days before the mud eruption, an earthquake of moment magnitude 6.3 hit the south coast of Central Java and Yogyakarta provinces killing 6,234 people and leaving 1.5 million homeless. At a hearing before the parliamentary members, senior executives of PT Lapindo Brantas argued that the earthquake was so powerful that it had created deep underground faults, allowing the mud to flow thousands of meters away, and that their company presence was coincidental, which should exempt them from paying compensation damage to the victims. If the cause of the incident is determined to be natural, then the government of Indonesia has the responsibility to cover the damage instead. This argument was also recurrently echoed by Aburizal Bakrie, the Indonesian Minister of Welfare at that time, whose family firm controls the operator company PT Lapindo Brantas.

However the UK team of geologists downplayed Lapindo's argument and concluded that the earthquake was merely coincidental. While it could have generated a new fracture system and weakened strata surrounding the Banjar-Panji 1 well it could not have been the cause of the formation of the hydraulic fracture that created the main vent 200 m away from the borehole. Additionally there was no other mud volcano reported on Java after the earthquake and the main drilling site is 300 km (186.5 miles) away from the earthquake's epicenter. The intensity of the earthquake at the drilling site was estimated to have been only magnitude 2 on Richter scale, the same effect as of a heavy truck passing over the area.

Legal case

On June 5, 2006, MedcoEnergi (one partner company in the Brantas PSC area) sent a letter to PT Lapindo Brantas which accused them of breaching safety procedures during the drilling process. The letter further attributes "gross negligence" to the operator company for not equipping the well bore with safety steel casing. Soon afterwards vice presidentJusuf Kalla announced that PT Lapindo Brantas and the owner, the Bakrie Group, must compensate thousands of victims affected by the mud flows. A criminal investigation was then started against several senior executives of the company because the drilling operation has put the lives of local people at risk.

Aburizal Bakrie frequently said that he is not involved in the company's operation and further detached himself from the incident. Even in his capacity as Minister of Welfare, Aburizal Bakrie was reluctant to visit the disaster site. Aburizal Bakrie's family business group, Bakrie Group, one of the owners of PT Lapindo Brantas, had been trying to distance themselves from the Lusi incident. Afraid of being liable for the disaster, Bakrie Group announced that they would sell PT Lapindo Brantas to an offshore company for only $2, but Indonesia's Capital Markets Supervisory Agency blocked the sale. A further attempt was made to try to sell to a company registered in the Virgin Islands, the Freehold Group, for US$1 million, which was also halted by the government supervisory agency for being an invalid sale. Lapindo Brantas was asked to pay about 2.5 trillion rupiah (about US$ 276.8 million) to the victims and about 1.3 trillion rupiah as additional costs to stop the flow. Some analysts predict that the Bakrie Group will emulate many US mining companies and pursue bankruptcy to avoid the cost of clean up, which could amount to US$ 1 billion.

On August 15, 2006, the East Java police seized the Banjar-Panji 1 well to secure it for the court case. The Indonesian environmental watchdog, WALHI, have meanwhile filed a suit against PT Lapindo Brantas, President Susilo Bambang Yudhoyono, the Indonesian Minister of Energy, the Indonesian Minister of Environmental Affairs and local officials.

After investigations by independent experts, police have concluded the mud flow was an "underground blow out", triggered by the drilling activity. It is further noted that the steel casing lining had not been used which could have prevented the disaster. Thirteen Lapindo Brantas' executives and engineers face twelve charges of violating Indonesian laws.

Current status

As of September 2, 2008, the mud flow is still ongoing. A study has found that the mud volcano is collapsing under its own weight, possibly beginning of caldera formation.. The researchers say the subsidence data could help determine how much of the local area will be affected by Lusi. Their research used GPS and satellite data recorded between June 2006 and September 2007 that showed the area affected by Lusi had subsided by between 0.5 meters [1.6 feet] and 14.5 meters [47.6 feet] per year. The scientists found that if Lusi continued to erupt for three to 10 years at the constant rates measured during 2007 then the central part of the volcano could subside by between 44 meters [144 feet] and 146 meters [479 feet] – 26 meters [85 feet] longer than a football pitch. They propose the subsidence is due to the weight of mud and collapse of rock strata due to the excavation of mud from beneath the surface. Their study has also found that while some parts of Sidoarjo are subsiding others are rising suggesting that the Watukosek fault system has been reactivated due to the eruption.

Workers helping to relocate families after new hot gas flows began to appear. The workers were taken to a local hospital to undergo treatment for severe burns. In Siring Barat, 319 more families have been displaced and in Kelurahan Jatirejo, 262 new families are also going to be affected by the new flows of gas. Protesting families took to the streets demanding compensations, which in turn added more delays to the already stressed detour road for Jalan Raya Porong and the The Porong-Gempol toll road.

The government has stated that their heart is with the people. Though the cabinet meeting on how to disperse the compensation has been delayed until further notice. Local official, Saiful Ilah, signed a statement announcing that "The government is going to defend the people of Siring." After this announcement all protests came to an end and traffic flow returned to normal an hour later.